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Full text of "The Morphology And Evolution Of The Apes And Man"

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THE NERVOUS SYSTEM                   •!&;>
It can be traced down to the lower part of the latter muscle into which it sinks. It also supplit- the sternc-and cleido-mastoid muscles. At the top of the neck it communicates with the vagus and cervical plex-i*. b"t not with the sympathetic cord.
It is essentially similar in all the Apes.
Hypoglossal Nerve.—The origin, course and relations are as in Man; and it likewise communicates vrith the vagus, sympathetic and lingual nerves. It sends the descendens hypoglossi to unite with the cervical nerves to form the ansa kypogio&s:. It also supplies the thyro-hyoid, genio-hyoid, genio-glossus and stylo-g:cs~*:i muscles. It is essentially similar in ail the Apes and Man.
In all the Apes the first four cervical nerves unite in a looped manner to form the cervical plexus, whose position and relations are as in Man. There are slight differences in the branches ; and the latter form cutaneous, muscular and communicating groups. The fourth cervical nerve communicates with the fifth.
The following table shows the branches in the Chimpanzee (fig. 54) :—
A.  Communicating Nerves (deep).
(1) To vagus (G.N.), accessory (XI), hypo-glossal (XII), from Cl and C2 and sympathetic.
B.  Muscular Branches (deep). Sterno-inastoid (S-M.) from C2. Trapezius  (Tra.) from C3 and C4. Levator anguli scapulae (L.A.S.) from 03.